1. Field of the Invention
The present invention relates to watermarking method and device, and more particularly a watermarking method which is capable of integrity authentication by identifying forgery/alternation of digital audio signals, and device thereof.
2. Description of the Related Art
Watermarking technology is used in various fields such as broadcasting monitoring, owner identification, authentication, fingerprinting for tracing illegal circulation, covert communication, copy control, etc. The requirements for watermarking technology used in these applied fields may differ for each field; however, in common, the difference between the original data and the watermarked data should not be identified by the human five senses.
Among these various applied fields, authentication is one of the applied fields which are recently gaining attention. Systematic research on authentication has been performed for a long period of time in the field of encryption. The first person to bring up the problem of authentication in the field of watermarking was Friedman (U.S. Pat. No. 5,499,294). He proposed that authentication for digital images will be possible by embedding an encrypted signature extracted as the characteristic value of an image into an image data. In such case, even if a single pixel of information is changed, it is impossible to detect the signature which corresponds to the embedded encrypted signature. Thus, no manipulation is allowed. In addition, Lin & Chang proposed an authentication method wherein the embedded data are not changed by harmless data manipulation such as JPEG compression, whereas the embedded data are changed by other attacks such as the addition, deletion or alternation, etc. of a part of the data.
Among the various applied fields of watermark, the present invention focuses on research on authentication. Research on the previously developed authentication technology was mainly directed to image and video, and there was almost no authentication technology related to voice signal and audio signal. Recently, as a voice recording device is changing from an analogue recording device into a digital recording device, authentication on audio signals is being required. Thus, along with the development of digital voice recording devices using voice recorders and MP3 players, the necessity of authentication is increasing.